I was in my local sporting goods store and I noticed on the rack a model 31 Remington,30in,solid rib full.When I looked closer at it the model number on the side was model 31-S? I have a field model,and a T/C trap model,What does the "s" mean. I never seen that before,and I would think if it was a skeet model it would be a 26" ,skeet or imp. cyl. barrel,not full? Any ideas,thanks.